We’ve been willingly plunging ourselves into extremely hot and cold water as a form of physical therapy since the days of the Roman Empire. Now, a project called the wa_sauna–which seems to stand for Washington Sauna–is making that age-old tradition mobile. It’s a floating boat that provides a steamy retreat, until you hop off the deck into the frigid waters of Seattle’s lakes.

Designed by the architects at goCstudio after raising money on Kickstarter, the minimalist retreat-barge is now fully operational–and goCstudio will be running events this summer on waterways around Seattle to try it out.

Its design seems so simple, it almost feels like you could build your own: the core platform is a pre-constructed aluminum frame, topped with marine-grade plywood. It’s able to float thanks to a network of 28 empty 55-gallon drums attached underneath. Atop that, the sauna is constructed with a stained plywood shell and cozy spruce interior. A simple wood-burning stove provides the heat and the steam, meaning the only thing that requires any power at all is the low-speed trolling motor, which runs on three 12-volt batteries and features a small built-in rudder for steering.

It’s surprisingly low-tech magic. And in fact, the most challenging part of development, the team tells us, was actually getting the sauna into the water. Towing the 14-foot, 4,500-pound structure just eight blocks was a three-hour ordeal, as it rolls precariously across dry land on just a few steel casters. Luckily, the vessel has better sea legs.

The wa_sauna is currently open for friends of the studio to visit on nice weekends. They’re also open to hosting events upon request.